:root {
  --bg: #FAFAFA;
  --bg-elevated: #FFFFFF;
  --bg-card: #FFFFFF;
  --border: #E5E5E5;
  --border-hover: #D4D4D4;
  --text-primary: #171717;
  --text-secondary: #525252;
  --text-muted: #A3A3A3;
  --accent: #2563EB;
  --accent-hover: #1D4ED8;
  --accent-ghost: rgba(37, 99, 235, 0.08);
  --accent-glow: rgba(37, 99, 235, 0.15);
  --green: #16A34A;
  --green-bg: rgba(22, 163, 74, 0.1);
  --red: #DC2626;
  --red-bg: rgba(220, 38, 38, 0.1);
  --orange: #EA580C;
  --orange-bg: rgba(234, 88, 12, 0.1);
  --yellow: #CA8A04;
  --yellow-bg: rgba(202, 138, 4, 0.1);

  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;

  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 12px 40px rgba(0, 0, 0, 0.12);
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: var(--font-sans);
  background: var(--bg);
  color: var(--text-primary);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

.app {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.header {
  background: var(--bg-elevated);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-inner {
  max-width: 800px;
  margin: 0 auto;
  padding: 0 24px;
  height: 60px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--text-primary);
  text-decoration: none;
}

.nav-links {
  display: flex;
  gap: 24px;
}

.nav-links a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  transition: color 0.2s;
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--accent);
}

.main {
  flex: 1;
  padding: 40px 24px;
}

.container {
  max-width: 800px;
  margin: 0 auto;
}

.panel {
  animation: fadeIn 0.3s ease;
}

.panel.hidden {
  display: none;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

.title {
  font-size: 1.75rem;
  font-weight: 700;
  margin-bottom: 32px;
  color: var(--text-primary);
}

.form-group {
  margin-bottom: 28px;
}

.label {
  display: block;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 12px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.input {
  width: 100%;
  padding: 12px 16px;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-family: inherit;
  background: var(--bg-elevated);
  color: var(--text-primary);
  transition: border-color 0.2s, box-shadow 0.2s;
}

.input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-glow);
}

.time-options,
.num-options {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.time-btn,
.num-btn {
  padding: 10px 20px;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: var(--bg-elevated);
  color: var(--text-secondary);
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
}

.time-btn:hover,
.num-btn:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.time-btn.active,
.num-btn.active {
  background: var(--accent);
  color: white;
  border-color: var(--accent);
}

.subject-options {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12px;
}

.checkbox-label {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 12px 16px;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all 0.2s;
  background: var(--bg-elevated);
}

.checkbox-label:hover {
  border-color: var(--accent);
}

.checkbox-label input[type="checkbox"] {
  width: 18px;
  height: 18px;
  accent-color: var(--accent);
}

.checkbox-label span {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.info-box {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px;
  margin-bottom: 28px;
}

.info-title {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 16px;
}

.info-grid {
  display: flex;
  gap: 24px;
}

.info-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
}

.info-value {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
}

.info-value.correct {
  color: var(--green);
}

.info-value.wrong {
  color: var(--red);
}

.info-label {
  font-size: 0.75rem;
  color: var(--text-muted);
  text-transform: uppercase;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 24px;
  border-radius: var(--radius-md);
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  border: none;
  text-decoration: none;
}

.btn-primary {
  background: var(--accent);
  color: white;
}

.btn-primary:hover {
  background: var(--accent-hover);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.btn-ghost {
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border);
}

.btn-ghost:hover {
  background: var(--bg-elevated);
  border-color: var(--border-hover);
}

.btn-lg {
  padding: 14px 32px;
  font-size: 1rem;
  width: 100%;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.test-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 16px;
}

.test-progress {
  font-size: 0.9rem;
  color: var(--text-secondary);
  font-weight: 500;
}

.timer {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-primary);
  font-variant-numeric: tabular-nums;
}

.timer-bar {
  height: 4px;
  background: var(--border);
  border-radius: 2px;
  margin-bottom: 32px;
  overflow: hidden;
}

.timer-fill {
  height: 100%;
  background: var(--accent);
  border-radius: 2px;
  transition: width 1s linear;
}

.timer-fill.urgent {
  background: var(--red);
}

.question-container {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 32px;
  margin-bottom: 24px;
}

.question-meta {
  display: flex;
  gap: 12px;
  margin-bottom: 16px;
}

.q-subject {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  background: var(--accent-ghost);
  padding: 4px 10px;
  border-radius: var(--radius-sm);
}

.q-year {
  font-size: 0.75rem;
  color: var(--text-muted);
}

.question-text {
  font-size: 1.15rem;
  font-weight: 600;
  line-height: 1.5;
  margin-bottom: 24px;
  color: var(--text-primary);
}

.options {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.option-btn {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 16px 20px;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: var(--bg-elevated);
  cursor: pointer;
  transition: all 0.2s;
  text-align: left;
  width: 100%;
}

.option-btn:hover {
  border-color: var(--accent);
  background: var(--accent-ghost);
}

.option-btn.selected {
  border-color: var(--accent);
  background: var(--accent-ghost);
}

.option-btn.correct {
  border-color: var(--green);
  background: var(--green-bg);
}

.option-btn.wrong {
  border-color: var(--red);
  background: var(--red-bg);
}

.option-label {
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  background: var(--bg);
  border: 1px solid var(--border);
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-secondary);
  flex-shrink: 0;
}

.option-btn.selected .option-label {
  background: var(--accent);
  color: white;
  border-color: var(--accent);
}

.option-text {
  font-size: 1rem;
  color: var(--text-primary);
}

.test-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  margin-bottom: 24px;
}

.question-nav {
  display: flex;
  justify-content: center;
}

.nav-dots {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  justify-content: center;
  max-width: 600px;
}

.nav-dot {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  border: 1px solid var(--border);
  background: var(--bg-elevated);
  color: var(--text-secondary);
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  display: flex;
  align-items: center;
  justify-content: center;
}

.nav-dot:hover {
  border-color: var(--accent);
}

.nav-dot.current {
  border-color: var(--accent);
  background: var(--accent);
  color: white;
}

.nav-dot.answered {
  border-color: var(--green);
  background: var(--green-bg);
  color: var(--green);
}

.nav-dot.skipped {
  border-color: var(--orange);
  background: var(--orange-bg);
  color: var(--orange);
}

.score-card {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 40px;
  text-align: center;
  margin-bottom: 32px;
}

.score-main {
  display: flex;
  align-items: baseline;
  justify-content: center;
  gap: 8px;
  margin-bottom: 8px;
}

.score-value {
  font-size: 4rem;
  font-weight: 700;
  color: var(--accent);
  line-height: 1;
}

.score-total {
  font-size: 1.5rem;
  color: var(--text-muted);
  font-weight: 500;
}

.score-percentage {
  font-size: 1.25rem;
  color: var(--text-secondary);
  font-weight: 600;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
  margin-bottom: 32px;
}

.stat-card {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 24px;
  text-align: center;
}

.stat-card.correct {
  border-color: var(--green);
}

.stat-card.wrong {
  border-color: var(--red);
}

.stat-card.skipped {
  border-color: var(--orange);
}

.stat-icon {
  font-size: 1.5rem;
  margin-bottom: 8px;
}

.stat-number {
  font-size: 2rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 4px;
}

.stat-card.correct .stat-number {
  color: var(--green);
}

.stat-card.wrong .stat-number {
  color: var(--red);
}

.stat-card.skipped .stat-number {
  color: var(--orange);
}

.stat-label {
  font-size: 0.8rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.actions {
  display: flex;
  gap: 12px;
  justify-content: center;
}

@media (max-width: 640px) {
  .subject-options {
    grid-template-columns: 1fr;
  }

  .stats-grid {
    grid-template-columns: 1fr;
  }

  .info-grid {
    justify-content: center;
  }

  .question-container {
    padding: 20px;
  }

  .score-value {
    font-size: 3rem;
  }
}